Fenestration members such as sliding glass patio doors and the like are well known in the art and are commonly used in residential dwellings, apartment units and the like. Such sliding glass doors typically comprise one or more enlarged glass panes carried in a surrounding metal, wooden or fiberglass frame adapted for sliding movement back and forth upon a lower track or rail. A vertical stile along one edge of the sliding door normally carries a lock assembly adapted for keyless operation from the indoor side of the door, and if desired, for keyed operation from the outdoor side of the door. This lock assembly typically includes one or more latch members for selective engagement with a matingly shaped latch keep mounted on the adjacent doorjamb for locking the door against unauthorized entry. An example of a sliding door lock assembly is reported in U.S. Pat. No. 4,754,624 (Fleming et al.). Fleming reports a lock assembly for sliding glass doors that displaces dual latch members toward and away from each other between locked and unlocked positions.
A drawback of traditional sliding door lock assemblies is that the force of closing the sliding door can cause the lock assembly to shift to a locked position. This is particularly common when the lock assembly becomes positioned at an intermediate point between a locked and an unlocked position when the door is open. The force of the closing door can cause the lock to shift from this intermediate point to the locked position. In this manner, a user can be locked out of a home without intentionally engaging the lock. The resulting lockout is not only an inconvenience, but can also create a significant safety issue for the user under certain circumstances.
U.S. Pat. No. 6,327,879 (Malsom) reports a lock mechanism including a strike element preferably coupled with a door frame and a catch assembly preferably coupled with a fenestration member slidably supported within the frame. The lock assembly provides a user some protection from lockout because the lock cannot be engaged unless the catch is in contact with the strike element. However, the lockout feature reported in Malsom is complicated, requiring multiple gears, cams and springs to properly operate. Further, Malsom does not report a lockout feature that can be deactivated if the user does not wish to use the lockout prevention feature.